1. Field of the Invention
The present invention relates to the manufacture of lites (glass sheets or glass panels) which are eventually stacked in relatively intimated, though spaced, relationship to each other.
2. Description of the Relevant Art
It is conventional to stand lites/glass sheets on edge substantially vertically and interleave a sheet of paper, such as craft paper, between the sheets. Such sheets are generally stacked upon a pallet and are enclosed by a relatively strong polymeric/copolymeric film, such as relatively transparent or translucent polyethylene film. The interleaved sheets of paper function to impede corrosion of glass, prevent scratches and damp shocks, thereby safeguarding the glass sheets, which otherwise may be broken or cracked by relative movement/collision therebetween, as when such stacked and palletized sheets are transported to an end user.
Interleaving a sheet of paper between glass lites has in the past been done manually and is, therefore, time-consuming and costly from a production standpoint.
U.S. Pat. No. 4,807,743 acknowledges the function of such paper sheets to impede corrosion of glass, prevent scratches, damp shocks and prevent glass sheet/lite breakage. However, this patent also recognizes that moisture which is absorbed by such large paper sheets can create chemical reactions with the glass which produce paper stains on the glass surfaces. Wrinkle patterns from the paper sheets are said to be transferable to the lites thereby rendering the same less attractive. Glass quality is also said to deteriorate as a result of surface weathering of the glass sheets due to moisture absorption by the paper sheets, particularly under high humidity conditions under which water droplets may form and drip upon the lites. This patent suggests as one solution to these problems the same conventional utilization of craft paper as spacer material, but associated therewith are bodies of desiccant material housed within an overwrap of the stacked glass. The overwrap is a polyethylene film having low water vapor transmission characteristics. While this patent proposes solutions to several problems, its disclosure is silent with respect to the continued conventionality of utilizing large sheets of paper as spacers between adjacent pairs of lites.
Another approach to protecting sheets of material against damage during stacking or packaging is found in U.S. Pat. No. 3,385,462 which first acknowledges the interposition of loose materials, such as straw, wool fiber and sawdust, between sheets of glass when they are packed for transportation, or to interpose sheets of relatively soft material, such as paper or corrugated cardboard. However, the patent goes on to state that these methods do not prevent surface damage to the sheets which may in some cases make them useless, particularly if they are of a very high quality glass or have been specially surface treated. This patent proposes the utilization of a plurality of spacing members, such as pads of polyurethane having coatings of pressure-sensitive adhesive on the opposite faces which contact the glass sheets. An alternative approach is the utilization of spacing members each having a head portion formed as a suction member and a stem portion which is relatively flat. Such pads or spacer members are positioned between the glass sheets. These spacers are costly because of the intricate configuration thereof and the amount of material associated with each, not to mention the high productivity costs involved in manually locating a plurality of such spacers between adjacent glass sheets.
U.S. Pat. No. 2,992,747 avoids the utilization of individual spacers of any type, yet protects the surfaces of glass sheets that are stacked together for storage, shipment or other handling by spraying or applying parting material, with or without filler, upon surfaces of the sheets to maintain the same spaced when in stacked relationship. Such parting material coatings adhere to the glass sheet surfaces and provide suitable space between adjacent surfaces of the stacked glass sheets. Problems associated with such protection involve air quality standards during application, but more importantly remains the end use task of removing the coatings incident to the utilization of the glass sheets.
U.S. Pat. No. 2,476,145 suggests electrostatically charging glass sheets as they travel along a conveyor through the utilization of a silk cloth roll. Each glass sheet is thereby electrostatically charged. The electrostatically charged glass sheets are conveyed through an atmosphere filled with wood flour which causes the particles of flour to be attracted to the charged surfaces of the glass sheets in a relatively thin uniform layer. By negatively electrostatically charging the wood flour, the latter will be attracted and retained for a sufficient time to achieve stacking and wrapping of the glass sheets.